Cleaning arrangement and method for cleaning a flexographic coating unit

Abstract

A cleaning arrangement for a coater that has a plate cylinder, the cleaning arrangement having a cleaning web, a tangential moving mechanism configured to controllably move the cleaning web in at least one direction in a plane defined by the cleaning web, a radial moving mechanism configured to controllably move the cleaning web in at least one direction out of the plane, and a controller coupled to the tangential and radial moving mechanisms which is configured to control the moving of the cleaning web into and out of contact with the plate cylinder in conformity with input signals received by the controller.

What is claimed is: 
     
       1. A method for cleaning a coating unit, comprising the steps of:
 interrupting coating operation by a means for spreading a coating substance onto the outer surface of a plate cylinder used to spread a coating substance onto workpieces, 
 using a radial moving mechanism to press a cleaning web against an outer surface of the plate cylinder for performing a cleaning operation, 
 rotating the plate cylinder to rub its outer surface against said cleaning web, 
 wetting the cleaning web before it comes in contact with the outer surface of the plate cylinder, 
 using a tangential moving mechanism in a direction tangential to said outer surface of the plate cylinder to bring an unused portion of said cleaning web to a location where it can be pressed against the outer surface of the plate cylinder, 
 directing an air knife from one or more blower nozzles, that are spaced from the plate cylinder and the impression cylinder, in an operating direction toward a nip formed between the plate cylinder and an impression cylinder to remove remnant wetting liquid from the outer surface of the plate cylinder by blowing the air downward toward the impression cylinder, 
 terminating cleaning operation, and 
 resuming coating operation during which said air knife acts on an upper surface of a workpiece exiting said nip to ensure the detaching of a front end of the workpiece from the outer surface of the plate cylinder as the workpiece exits said nip. 
 
     
     
       2. A method according to  claim 1 , comprising the further step of:
 after said use of the radial moving mechanism to press the cleaning web against the outer surface of the plate cylinder, and before a subsequent use of the tangential moving mechanism to bring an unused portion of the cleaning web to a location where it can be pressed against the outer surface of the plate cylinder, using the radial moving mechanism to temporarily detach the cleaning web from the outer surface of the plate cylinder. 
 
     
     
       3. A method according to  claim 1 , comprising the further step of:
 wetting a portion of said cleaning web before—or simultaneously with—pressing it against the outer surface of the plate cylinder. 
 
     
     
       4. A method according to  claim 3 , comprising:
 after pressing the wetted portion of the cleaning web against the outer surface of the plate cylinder, pressing a dry portion of the cleaning web against the outer surface of the plate cylinder. 
 
     
     
       5. A cleaning arrangement for a coater that comprises a plate cylinder and an impression cylinder, the cleaning arrangement comprising:
 a cleaning web that has a cleaning surface and a back surface, 
 a tangential moving mechanism configured to controllably move said cleaning web in at least one direction in a plane defined by said cleaning web, 
 a radial moving mechanism configured to controllably move said cleaning web in at least one direction out of said plane, 
 a wetting arrangement for wetting the cleaning web with wetting liquid before it comes in contact with the outer surface of the plate cylinder, 
 a controller coupled to said tangential and radial moving mechanisms, said controller being configured to control the moving of said cleaning web in conformity with input signals received by said controller, and 
 one or more blower nozzles with an operating direction directed toward a nip formed between said plate cylinder and said impression cylinder, said one or more blower nozzles being spaced from the plate cylinder and the impression cylinder and forming an air knife directed downward toward the impression cylinder, 
 wherein the one or more blower nozzles are arranged before the cleaning arrangement in the operation direction of the plate cylinder for removing remnant wetting liquid from the plate cylinder during cleaning of the plate cylinder and for directing air toward an upper surface of a workpiece exiting said nip for detaching of a front end of the workpiece from the outer surface of the plate cylinder as it exits the nip during coating operation, 
 wherein said radial moving mechanism comprises an inflatable cushion on the back surface side of said cleaning web, and a pressurized air dosing arrangement comprising a controllable valve for controlling supplying of pressurized air for inflating and deflating said inflatable cushion during said cleaning operation and for supplying of pressurized air to the one or more blower nozzles during said coating operation, and 
 wherein the tangential moving mechanism comprises a feed roller, a spool parallel to said feed roller, and a motor configured to rotate at least said spool for winding the cleaning web unwound from said feed roller onto said spool, and a motor configured to rotate the feed roller. 
 
     
     
       6. A cleaning arrangement according to  claim 5 , wherein:
 said plane is defined by a portion of said cleaning web drawn between said feed roller and said spool. 
 
     
     
       7. A cleaning arrangement according to  claim 5 , comprising:
 one or more wetting nozzles with an operating direction directed towards the back surface of said cleaning web, and 
 a wetting liquid dosing arrangement configured to controllably deliver wetting liquid through said one or more wetting nozzles towards the back surface of said cleaning web. 
 
     
     
       8. A cleaning arrangement according to  claim 7 , wherein:
 the one or more wetting nozzles are located between said feed roller and spool, with said operating direction being towards a planar portion of said cleaning web drawn between said feed roller and said spool.